The present invention is directed to an explosive powder charge operated driving device for driving fastening elements and the like into a receiving material. The device includes a housing with a driving piston located within the housing and having a radially extending shoulder at the rear end of the shank part of the driving piston with the shoulder facing in the driving direction. The driving piston is located within a barrel which is displaceable relative to the housing in the driving direction of the piston. A locking member is mounted on the housing and extends into the path of the shoulder on the driving piston. The part of the locking member which engages the shoulder extends perpendicular to the axis of the driving member. A retaining member mounted on the housing includes a support shoulder for retaining the locking member within the housing. At least a portion of the support shoulder overlaps the locking member when it is positioned within the housing.
In explosive powder charge operated driving tools including a driving piston for transmitting the explosive force of the charge to a fastening element to be installed, the driving piston after a fastening element has been driven into a receiving material, must be displaced rearwardly within the barrel into a position ready to drive another fastening element.
In a known driving device disclosed in CH-PS No. 533,037, a locking member is positioned in the housing of the driving device and is provided for moving the piston member in the axial direction opposite to the driving direction by contacting a radially extending shoulder on the piston. After a fastening element has been driven, by moving the barrel in the driving direction with the locking member bearing against the shoulder on the driving piston, the piston is displaced to the rear end of the barrel so that it can be moved rearwardly with the barrel into the ignition position.
The locking member is retained in the operating position by a support shoulder of a retaining member forming a part of the tool housing. To replace the driving piston, the locking member must be removable and this is effected by removing the retaining member which is in the form of a screw. The removal of the retaining member requires an auxiliary tool and, in addition, requires considerable manipulative effort due to the need to completely remove the retaining member. Similarly, additional effort is needed for the insertion and retention of the locking member by the retaining member.